Ceramic matrix composites (CMC) are used for making components for relatively high-strength (for example, high-pressure), high-temperature applications such as for various components in gas turbines and the like. The components may be fabricated by laminating multiple layers of ceramic fibers in a ceramic matrix. In such constructions, the ceramic fibers effectively act as load bearing members and the ceramic matrix effectively acts as a load transferring mechanism for transferring the load between the load bearing members when the CMC component is stressed.
Due to mechanical and/or thermal loading, the stress state in a CMC component can be multi-axial, for example, including both in-plane bending stresses and through-thickness stresses. The in-plane bending stresses may tend to peak, for example, at or proximate a CMC component surface and decrease to about zero at or proximate the mid-thickness position of the CMC component. Contrary to the in-plane bending stresses, the through-thickness stresses may tend to peak, for example, at or proximate the mid-thickness position of the CMC component and drop to about zero at or proximate the CMC component surface.
CMC components are typically made, for example, from stacks or layups of 1-directional (e.g., unidirectional) fabrics or 2-directional (e.g., bidirectional) fabrics. Ceramic matrix composites fabricated with 1-directional fabrics are relatively very strong in the fiber direction (e.g., direction of the unidirectional fiber tows), but are relatively weak in the direction transverse to the unidirectional fiber tows. 2-directional fabrics have fiber tows running, for example, in two directions. Such 2-directional fiber constructions help to strengthen the ceramic matrix composite in the two directions corresponding to directions of the bidirectional fibers tows. However, the bidirectional fiber tow crossover regions of the fabric can create weak areas from stress concentration. Additionally, fiber volume fraction ratios can be relatively low due to ceramic matrix infiltration and the fibers being split into two different directions. As such, 2-directional fabrics can have lower in-plane strength compared to 1-directional fabrics in the fiber direction. Additionally, both 1-directional fabrics and 2-directional fabrics have relatively low through-thickness strengths as there are no fibers extending in the direction normal to the fabric layer.
Accordingly, it is desirable to provide CMC components with improved through-thickness strength without compromising in-plane strength and methods for fabricating such CMC components. Furthermore, other desirable features and characteristics of the present disclosure will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanied drawings and this background.